Colorimetric surface plasmon resonance imaging (SPRI) biosensor array based on polarization orientation.

A colorimetric surface plasmon resonance (SPR) imaging biosensor array based on polarization orientation rotation is presented in this paper. It measures the spectral characteristic variations caused by the steep phase difference between the p- and s-polarization occurring at surface plasmon excitation. It provides one-order of magnitude sensor resolution improvement comparing to existing phase-sensitive SPR imaging sensors and the two-dimensional (2D) sensing capability of the imaging sensor enables multiplex, high throughput array based simultaneous detection for a range of different bio-molecular interactions. Experiments on the binding interactions detection between anti-bovine serum albumin (anti-BSA) and BSA antigen have been performed. All binding interactions occurred at 5×4 protein array were real-time monitored simultaneously. A sensor resolution of 8.26ng/ml (125pM) has been demonstrated, which is one-order of magnitude (12 times) better than the detection limit reported by existing phase-sensitive SPR imaging sensors in the literature, while no time-consuming phase modulation and phase extraction processes are required. Furthermore, the optical colorimetric image read-out of the sensor is easy to be identified by the end users comparing to conventional intensity or phase information. The colorimetric SPR imaging biosensor array can find promising potential applications in high throughput clinical disease diagnosis, protein biomarkers screening and drug screening.

Multiplex spectral surface plasmon resonance imaging (SPRI) sensor based on the polarization control scheme.

A two-dimensional (2D) spectral SPR sensor based on a polarization control scheme is reported in this paper. The polarization control configuration converts the phase difference between p- and s- polarization occurring at surface plasmon resonance (SPR) into corresponding color responses in spectral SPR images. A sensor resolution of 2.7 x 10(-6) RIU has been demonstrated, which corresponds to more than one order of magnitude resolution improvement (26 times) comparing to existing 2D spectral SPR sensors. Multiplex array detection has also been demonstrated with the spectral SPR imaging sensor. In a 8 x 4 sensor array, 32 samples with different refractive index values were monitored simultaneously. Detection on bovine serum albumin (BSA) antigen-antibody binding further demonstrated the multiplex detection capability of the 2D spectral SPR sensor for bio-molecular interactions. The detection limit is found to be 21 ng/ml, which is 36 times better than the detection limit previously reported by phase imaging SPR sensors. In light of the advantages of high sensitivity, 2D multiplex detection and real-time response, the spectral SPR imaging sensor can find promising applications in rapid, high throughput, non-labeling and multiplex detection of protein array for proteomics studies, biomarker screening, disease prognosis, and drug discovery.

Dynamic quantitative photothermal monitoring of cell death of individual human red blood cells upon glucose depletion.

Red blood cells (RBCs) have been found to undergo "programmed cell death," or eryptosis, and understanding this process can provide more information about apoptosis of nucleated cells. Photothermal (PT) response, a label-free photothermal noninvasive technique, is proposed as a tool to monitor the cell death process of living human RBCs upon glucose depletion. Since the physiological status of the dying cells is highly sensitive to photothermal parameters (e.g., thermal diffusivity, absorption, etc.), we applied linear PT response to continuously monitor the death mechanism of RBC when depleted of glucose. The kinetics of the assay where the cell's PT response transforms from linear to nonlinear regime is reported. In addition, quantitative monitoring was performed by extracting the relevant photothermal parameters from the PT response. Twofold increases in thermal diffusivity and size reduction were found in the linear PT response during cell death. Our results reveal that photothermal parameters change earlier than phosphatidylserine externalization (used for fluorescent studies), allowing us to detect the initial stage of eryptosis in a quantitative manner. Hence, the proposed tool, in addition to detection of eryptosis earlier than fluorescence, could also reveal physiological status of the cells through quantitative photothermal parameter extraction.